There's a multitude of ways to build a performance machine, but at the core of the whole enterprise we all want the same thing: to get the most out of what we have. In fact, you can boil down what we want our combos to be in one word, optimized. The dictionary defines it as: "To make something function at its best or most effectively, or use something to its best advantage." Good word, eh? In fact, it's a word that came up frequently during our recent discussion with Chris Alston, proprietor of Chassiworks and maker of the VariShock line of adjustable shock absorbers. We set out to explore single-adjustable versus double-adjustable shocks and also touch on why both of them far outclass nonadjustable shocks when it comes to optimizing a performance automobile.
What Does A Shock Absorber Do?Dissertations have been written on the subject, but the answer is actually pretty simple. In short, shocks absorbers control how the suspension works. While springs hold up the car, supporting its weight, shock absorbers damp the oscillations that occur as the springs move up and down. They never totally remove the oscillations, but in more simple terms, shocks control the bounce that springs would normally exhibit.
What's Wrong With Regular Old Shocks?We admit that this is something of a strawman argument, but since plenty of people buy traditional nonadjustable shocks, we felt like it was worth tackling. The bottom line is that an off-the-shelf, nonadjustable shock has the wrong damping for your car-period. Actually, there's one exception to this rule. If you've got a totally stock machine with everything in perfect working order, just as it rolled off the assembly line, and you buy a shock made for this arrangement, you're probably in decent shape. But how many of us are dealing with totally bone-stock setups?
Anything that has an effect on the suspension means the shock damping is wrong-bigger tires, more powerful brakes, lowering the vehicle, changing air pressure in the tire, literally anything-including changes in driver style. As soon as you change it, the shock is wrong. Of course that sort of belies the point, because in this arena, most of us as dealing with nonstock setups of one type or another, and we're more than likely driving our classics far beyond what their creators ever imagined.
The number of variables is extensive, and choosing the right nonadjustable shock for any of these many combos is damn near impossible. "If I could guess what your valving should be," quipped Alston, "I'd quit making shocks and buy Lotto tickets."
The bottom line? Anything that changes or affects the suspension means the system isn't optimized. And remember, optimized is what we all want.
What We Did
Talked with Chris Alston about the pros and cons of single- and double-adjustable shocks
Double-adjustable shocks are the best way to optimize your car's suspension
It's actually a bit deceptive to refer to a shock like VariSshocks's QuickSet 1 as a single-adjustable shock. It is single-adjustable in that there is one knob to turn through 16 clicks of adjustment. On the other hand, each click adjusts both rebound damping (the shock coming apart) and compression damping (the shock coming together) at the same time. "It's just the way the ports are inside the shocks," explains Alston. "The oil flows both ways through one adjuster." Some single-adjustable shocks, Alston went on, adjust only one half the equation-either rebound damping or compression damping, but not both. "Ours adjust both together-both get stiffer, and you can adjust both ends. If you take a look at the accompanying Single-Adjustable VariShock dyno chart, this is clearly illustrated. As rebound damping (pulling apart) gets stiff, so does the compression damping (coming together). The compression damping doesn't get as stiff as the rebound damping, but it does go up in proportion to the latter, making the whole shock stiffer or softer. "They're actually a phenomenally cool tool to adjust a car's suspension, and the fact that you can adjust it at all means you get closer to where you need to be," Alston declared, "but it's better if you can adjust both sides."
On the other hand, double-adjustable shocks like VariShocks QuickSet 2 route the shock's internal oil through both adjusters. When it comes to how the oil flows, it's a completely different pathway-the valving is way more complex, and that complexity, along with the adjustability it permits, is what you're paying for when you step up to double-adjustable shocks. "The lines are completely independent," said Alston. "That's why you can have full stiff on one setting and full soft on the other setting." The range of adjustment is also much more vast. Instead of the QuickSet 1's 16 adjustments, the QuickSet 2 provides an amazing 256 adjustment combinations. Because both types of damping can be adjusted separately, the range is exponentially greater than that found in a single-adjustable shock. Again, look at the QuickSet 2 shock dyno chart and see how great the range of settings is-from very soft, as in less than 100 pounds of force, all the way up to 500 pounds of force and everything in between.
These settings-rebound damping and compression damping-operate separately in the car. You might think the two are related, but in fact they actually don't have anything to do with each other. "The most obscene example of this is a drag race car," Alston continued, "and the most extreme is the front of the car." For instance, at launch, the shock needs to come apart as fast as possible for maximum weight transfer, but not so fast that when it runs out of travel, it shocks the chassis hard enough to unload the tires and unhook the car. "Much more misunderstood is when the car comes down and hits bottom," says Alston. "Also, the tire can unload if the front end settles down too quickly and hits the bumpstop, resulting in that bobble many racers experience at the gear change. "I've worked on cars that picked up a couple of tenths from front shock tuning" Alston says. "When it comes to drag shocks, "People think the softer the better, but they're wrong."
On the other hand, the benefits of adjustability aren't only for those who burn up the straight line. "Drag racers don't have the extreme loads caused by turning," Alston began. "On the other hand, those who go in for turn-oriented events like autocross don't have the extreme acceleration loads to deal with. The goal there is to determine how to transfer weight from side to side.... you don't want to transfer more weight than the car can use." Again, being able to separately adjust rebound and compression damping is a valuable tool to achieving this. "Not being able to adjust them separately," Alston said, "is like adjusting timing and jets together. It's great if you actually need more or less of both at the same time, but not so much if they need different settings." Again, the settings are independent, and you have more range. "They're much more sophisticated," Alston summed up, "and they're one of the easiest things to adjust on a race car.
A Word About Springs
Ostensibly, this article is about single- versus double-adjustable shock absorbers. On the other hand, it would be remiss of us to write an article about selecting shock absorbers without at least briefly discussing springs. Given all the variables involved, you're not going to be able to truly optimize your suspension unless you can dial in shock valving and spring rate. Alston puts it more bluntly: "The biggest problem with shocks is the wrong spring."
Focusing on coilovers, though the same principles apply to coil spring cars, he continues, "The biggest problem with coilovers is you have to support the car's weight-which is the spring's primary job-but you have to do it at the proper ride height." With the car done and sitting on the ground, you must check to see if the shock is sitting within its eye-to eye ride height range. If it's sitting too short, you need a stiffer spring. If it's too long, you need a softer spring. In both cases, you're looking to ensure that the shock has the amount of travel that's correct for the application. Minor adjustments to this height can then be made with spring preload. In general, preload is employed when lighter-than-standard springs are used. Remember, though, that preload is a subtle adjustment; too much can limit spring travel and compromise ride quality. Alston provides a wide selection of springs as well as guidelines for choosing the proper coils and for setting ride height for a variety of driving scenarios.
We all want the most from our machines, whether it's putting power to the pavement or making rapid directional changes through a maze of cones. No performance car can be all it can be without optimized suspension, and the road to optimization leads through adjustability. The more tuning choices you have, the better your chance of scoring a sweet-handling ride that helps cut tenths off your time. Our expert source Alston brought the advantage of double-adjustable shocks into clear view. "It's a tremendous advantage because you can get them to work on the car. And there's a 99 percent chance to get it right." The only disadvantage, if you want to call it that, is that you have to take the time to dial in your shocks. But since the result, with a little work, is a suspension that's optimized, we like those odds.